The Brief

A rare ring of light surrounding a galaxy nearly 590 million light-years from Earth has been discovered by a space telescope that scientists hope will uncover more cosmic phenomena throughout the universe, the European Space Agency announced on Monday.

The ring of light, known as an Einstein Ring, was discovered in September 2023 by Euclid, a space telescope on a six-year mission to map out the cosmos by observing billions of galaxies. Photos of the Einstein Ring show a bright ball of light in the center with a bright, cloudy ring around it.

The ring is surrounding NGC 6505, a galaxy that astronomers say is nearby, though it is hundreds of millions of light-years away.

NGC 6505 itself is not new to scientists and has been studied since the 19th century, Jacqueline McCleary, assistant professor of physics at Northeastern University says. The Einstein Ring, which had never been seen around this galaxy before, was suddenly easy to find because of Euclid's high resolution and sensitivity.

"You'd think that after generations of telescopes have looked at this thing for a century and change, we'd have figured out everything that there is to know about it, right? Wrong," McCleary tells NPR. "With other previous generations of telescope, this Einstein Ring was essentially drowned out by the light of this big galaxy."

The first known Einstein Ring — named after Albert Einstein, who predicted the bending of light through his theory of relativity — was discovered in 1987. Several have been discovered in the decades since, though it is unclear how many exist.  

A close up of the center of galaxy NGC 6505 with the Einstein Ring around it.

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ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre, G. Anselmi, T. Li

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European Space Agency

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An Einstein Ring is a ring of light around a form of dark matter, galaxy or cluster of galaxies, says Mustapha Ishak, an astrophysics professor at the University of Texas at Dallas. When light from a galaxy bends while moving past a massive object, such as another galaxy or cluster of galaxies, and reaches the telescope, this perfect alignment of all three makes the ring visible to the observer.

NGC 6505 is in alignment with another galaxy that is 4.42 billion light-years away and has never been observed and does not have a name, the ESA says.

"It looks to us like a ring because light is focused at that place in the shape of a ring," Ishak tells NPR.

They are not visible to the naked eye and can only be seen with a telescope like Euclid.

An Einstein Ring is also considered a strong gravitational lensing pattern, says Xiaosheng Huang, a physics and astronomy professor at the University of San Francisco. Gravitational lensing is when a massive object warps time and space, causing light to become distorted and bend as it moves around the object.

"This effect can result in several types of image configurations," Huang tells NPR about strong gravitational lenses, adding that the Einstein Ring is the most striking one.

The alignment creating the Einstein Ring will remain for some time, allowing astronomers to continue studying it, Ishak says. And telescopes like Euclid likely will give scientists a better understanding of dark matter, invisible matter that has gravitational effects, Huang says. But McCleary hopes it will lead to more "dramatic discoveries" and give scientists a peek into the mysteries of the universe.

"We'll be able to study distant old galaxies from early in the universe's history in far better detail and in far greater numbers than we have been able to up to this point," McCleary says.

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